(1) Field of the Invention
The present invention relates to a method for optimally routing a specific service in a network, and a server and a routing node which are used in the network. For instance, the present invention relates to a technique, under a circumstance where a server (master) which provides a specific service and a group of servers (mirrors) which reflect the same service contents as those provided by the server and provide the same service content by means of another server are present, the technique being suitable for making an access to a server considered to be optimal by a terminal, without the terminal becoming aware of positions (addresses) and operating status conditions of the servers.
(2) Description of the related Art
Current measures against a circumstance—where servers providing various services in a network, such as the Internet, are present and where accesses concentrate on a service—is a method for providing only identical service contents from another server located physically distant from the current server in the network and causing a user to select a destination and make an access to the destination. There is also a method for transferring an access to an optimal destination among load balancers connected to a server which provides a specific service.
According to the former method, the user must know the location of an appropriate service. Although there is also a location where a list of services is provided, a choice is left to the user, and therefore a problem of failure to attain efficient distribution of load exists. Moreover, information concerning which one of the servers in the list suspends provision of a service is not provided as well, and hence another problem of occurrence of a failure to obtain the service to which an access has been made also arises. In order to cause the terminal to automatically ascertain the information, the volume of information which must be collected becomes enormous, and hence automatic ascertainment of the information is practically impossible.
In contrast, according to the latter method, the load balancer must ascertain specifics of a server connected to the load balancer. However, even when a server is additionally provided, the load balancer does not automatically recognize the added server. For this reason, information concerning the added server must be provided to the load balancer. Moreover, when the load balancers are remotely located in the network, an optimal destination may change according to the status of the network. Since the load balancers do not ascertain the internal status of the network, there may arise a case where effective distribution of loads cannot be realized.
In addition, techniques proposed in Patent Documents 1 and 2, which are provided below, are available as conventional techniques.
The technique described in Patent Document 1 is for newly providing an attribute pertaining to band information to a routing protocol; notifying a border router in a network of band information concerning traffic having flowed in from another network, in conjunction with the routing information; and notifying a border router of another network of band information concerning traffic having flowed out from the network. As a result, according to the technique of Patent Document 1, band information, which can be input, can be automatically notified to all border routers with a small capital investment and minor adaptations, thereby saving labor of a network administrator and preventing occurrence of human errors.
Meanwhile, the technique described in Patent Document 2 relates to a method for managing a distribution-type database. On the basis of a server information management table into which a plurality of servers are classified (grouped) according to applications (services), a server is selected. At that time, a load table may be provided for each server, and a server having the lowest load may be selected. Alternatively, a table concerning service conditions of storage mediums (disks, tapes, or the like) of a plurality of servers may be provided, and a server having the largest available disk space selected. In addition, an application-specific information retrieval key and a server ID where information is to be stored have been registered as a retrieval-key-and-server-ID table in a storage management server. On the basis of only one service request from a user, the user can utilize a required service without becoming aware of the server.
Patent Document 1
JP-2002-374293A
Patent Document 2
JP-HEI6-259308A
However, according to the technique described in Patent Document 1, a band of a network can be managed. However, control operation for distributing loads cannot be performed by changing an access address to a server on which accesses are concentrated.
According to the technique described in Patent Document 2, an optimal server can be selected in accordance with the load of a server and the availability of storage capacity. Information concerning what type of a server is available as a database and information concerning natures of information items belonging to respective servers must be previously stored in the server information management table. Specifically, loads of the servers and the availability of storage capacity are mere objects of updating.
In the world of a network, this technique is identical with the method that has already been put into practice by means of the above-described load balancers. Therefore, the technique encounters the same problem as that mentioned previously. Patent Document 2 discloses that the server information management table can also be given to the router. However, even when a router is simply given server management information, the network cannot uniquely select an optimal destination without sharing or updating information concerning a group of servers in the network by automatically ascertaining the information and without the user becoming aware of service contents currently provided in the network and operating conditions.
The present invention has been conceived in view of the problems set forth and aims at enabling sharing and updating of information (positional information, service operation status conditions, or the like) concerning a group of servers in a network by automatically ascertaining the information within the network (a router or the like), and enabling the network to uniquely select an optimal destination without a user becoming aware of positional information concerning the server group and service operation status conditions, to thus effectively distribute accesses from a large number of usr terminals.